1. Field of the Invention
The present invention relates generally to sawmill equipment, and more particularly to an apparatus and method for ripsawing a cant to remove the wane edges therefrom and expose an optimum usable board area.
2. Description of the Prior Art
In sawmill operations, an incoming log is typically cut along a number of parallel, axial planes to yield a number of irregularly shaped planks referred to as "cants." The length of the cant is determined by the length of the log from which it was cut and is the same for all cants cut from the same log. The width of each cant, however, will vary depending on the particular section of the log which was cut. Cants which were derived from the central core of the log will be much wider than those derived from the edges of the log. Moreover, the cants will generally taper in one direction corresponding to the lessening diameter of the tree toward its top.
A cant will generally have two parallel, cut faces resulting from the initial ripsawing of the log, as well as a pair of irregular edges corresponding to the outer perimeter of the log. These rounded or beveled edges are referred to as "wane" edges and must be removed before finish cutting the cant into boards.
An important concern in operating a sawmill is optimizing the recovery of boards from a given log. Normally this will mean maximizing the total board feet of lumber derived from each log, although it may mean recovering a maximum number of boards of a certain length or having some other characteristic which makes them particularly valuable. Regardless of the particular optimization criteria employed, it is not obvious from examining an unfinished cant how to optimize the cutting of the cant into individual boards. For that reason, it would be desirable to provide a method and apparatus for automatically removing the wane edges from a cant to expose an optimum usable board area. It would be particularly desirable if the machine and method were capable of simultaneously sawing the cant into a plurality of individual boards having optimum dimensions.
U.S. Pat. No. 4,086,496 describes a machine for optimally sawing cants which comprises a first conveyor for transporting the cants transversely beneath an optical scanning system. The cants are fed to a second conveying system which delivers them axially beneath a pair of rotary sawblades. The distance between the sawblades may be adjusted in response to the profile determined by the optical scanning means, and the cant is initially oriented to pass through the sawblades at the optimal orientation. Although generally functional, it is very difficult to maintain the proper orientation of the cant as it is advanced beneath the sawblades. Thus, the cant is able to fall out of alignment and the resulting edges are neither optimum nor straight.
Other devices for optimally trimming the wane edges from cants are disclosed in U.S. Pat. Nos. 3,970,128; 3,963,938; 3,983,403; and 3,890,509. A device for removing a single wane edge from a cant prior to ripcutting is disclosed in U.S. Pat. No. 4,196,648.